Ways of Drilling Wastes Utilization Using Ecologically Safe Materials

Handling of the industrial waste, including drilling waste is still one of the leading fields in the ecology area. The article considers utilization way of the bore mud consisting in application of safe components allowing getting of the ground suitable for the reclamation of disturbed lands. There was revealed that the content of physical clay (d < 0,01 mm) in the control sample (bore mud) is 6,58%, when applying the mixture of components in the bore mud. The decrease of physical clay is observed in the ground of A type (2 times) and B and C types (3 times). In the same time, in the grounds of all types, hydrophysical properties improve and gelation takes place. Composition of the studied total forms of heavy metals was on the level of maximum allowable concentrations for loam. Manganese concentration in the control sample was in the range from 69 to 93 mg/kg. Water extract from the grounds of all types has very strong influence on the test objects (Daphnia magna Straus), class of hazard for the environment is IV.


Introduction
Handling of the industrial waste, including drilling waste is still one of the leading fields in the ecology area. Nowadays the main ways of drilling waste handling are thermal treatment and utilization (solidification, capsulation) with the following obtaining of production.
The accepted technologies of the bore mud utilization, as a rule, provides for the collection, accumulation and/or storage of the drilling waste in mud pits/temporary sectional tanks. However, despite such measures as dike of the mud pits, hydroisolation of their bottom and walls, the reliable protection of environment from the contamination with drilling waste is not provided [1,2].
In the process of well drilling the transformation of source raw material in the drilling waste takes place. As the result, liquid phase of the drilling waste forms -bore waste waters and used waste drilling fluid, solid phase -bore mud [7]. The bore muds are the fluid paste-like mass of dark-gray color with metallic tint. It is greasy by touch and has oil smell. Density of the bore mud is determined by the density of the drilling solution and drill cuttings. In the Western Siberia density of the bore mud varies from 1.3 to 2.2 g/cm 3 [3].
Viscosity (opposite property of the fluidity) is 0.1-4.5 Pa x s. Fluidity increases with the increase of water content and in case of poor solution purification. Dewatered bore muds loose fluidity and ground easily into the powder [3].
The studies of granulometric composition have shown that size of the bore mud particles are from 10 to 500 mkm. Moreover, bigger particles correspond to the drilling cuttings and the small ones to bentonite. PSD curve has two maximums. One maximum corresponds to the particles with a size 20-30 mkm, another one -200-300 mkm [3].
The main objects of pollution during the well drilling are geological environment (underground waters), hydro-lithosphere (open reservoirs, bottom of water areas, soil and vegetation cover) [8,9,10].
Accumulating in the soil layer, polluting components of drilling fluids lead to the loss of soil fertility: soil de-structuring, emergence or strengthening of erosion processes, decrease in the biological activity of the soil and its ability to self-cleaning. The most dangerous are alkaline mineralized waste muds and drill cuttings, the content of oil and oil products. The migration of toxic salts of components (ions of chlorine, sodium, sulfate ions, hydrogen bicarbonate ions) and oil products, both in vertical and horizontal directions, leads to deterioration of soil properties: the waterair regime of the soil is disturbed, the concentration of soil solution increases, sodium in MAC, microflora is inhibited, which makes the soil unsuitable for plant growth. This leads to the destruction of existing ecosystems on the territory, followed by contamination of adjacent environments [11,12].
Influence of the drilling waste on the natural objects can not only be expressed in toxic effect on the biosphere but also in disturbance of ecological balance of biotypes of different trophic level during their interaction with abiotic environment bearing the mechanism of functional ecosystem damages [13,14].
Nowadays various ways of bore mud utilization are offered based on the application of different technologies which finally lead to the forming of significant number of secondary wastes from the utilized bore muds which are in turn determine the necessity of planning of the independent ways of handling these wastes or to the forming of such production volumes which can't be in demand and are placed in the environment or require unreasonably high financial costs.

Materials and Methods
Source raw material for the soil is bore mud forming: a) during the drilling of field wells and easers on the oil and gas deposits using the mud pits; b) during the drilling of field wells and easers on the oil and gas deposits using the temporary sludge tanks; c) during the drilling of field wells and easers on the oil and gas deposits by pit-free drilling. The bore mud is mainly solid drilling waste and together with the drilling cuttings it includes all chemical compounds used for the preparation of the drilling fluids.
Materials used for the production of soil should correspond to the requirements of the effective regulatory documents. The choice of components and their number is stipulated by economic expediency, ecological properties of the obtained material and availability of the components.
Materials used for soil production:  quarry sands, commonly mined in the following ways: hydraulical placement method; drypowder method.  astringent: Portland cement.  aluminosilicate sorbents: glauconite; diatomite.  meliorating material: gypsum; phosphogypsum. Components of the soil and their ratio in it are selected in the course of laboratory studies on the basis of the results of chemical-analytical studies of the bore mud samples. The resulting soil consists of types and includes the following components: Soil type A: meliorating material and aluminosilicate sorbents; Type B soil: reclaiming material, aluminosilicate sorbents, quarry sand; Soil type B: meliorating material, binder, aluminosilicate sorbents, quarry sand. Laboratory and instrumental studies of the obtained soil during the utilization of the bore mud were carried out in an accredited testing laboratory [15,16,17,18].

Results
The bore muds are the fluid paste-like mass of dark-gray color with metallic tint. It is greasy by touch and has mixed smell. Density of the bore mud is determined by the density of the drilling solution, drill cuttings and humidity.
The main component of the bore muds -drilling cutting consists of the clay particles and sand (but in less volume) which determine its mechanical properties. When drying up (about 20% of humidity) the bore mud is solid and firm. During the further drying these pieces crack and disintegrate. Moistening leads to quick softening of pieces or the powder and change of mass into the viscoplastic and later fluid state.
Granulometric composition of the bore mud and obtained soil of different types is in the figure 1. Content of physical clay (d  0,01 мм) in the control sample (bore mud) is 6.58% when applying the mixture of components to the bore mud, we observe the decrease of physical clay in the type A soils by 2 times and in types B and C soils by 3 times. At the same time hydrophysical properties improve in all types of soils and gelation takes place.
Composition of heavy metals in the samples of bore mud and obtained soil of various types is given in the figure 2. The content of the studied gross forms of heavy metals was at the level of maximum allowable concentrations for loam. The concentration of manganese in the control sample was 200 mg kg, while the value of this element in the utilized bore mud was in the range from 69 to 93 mg/kg. In the process of utilization of the bore mud, the aluminosilicate sorbent was introduced, which has a high sorption capacity with respect to manganese ions.
The prospect of using the sorbent is conditioned on its adsorption and cation-exchange properties, which allows it to be used to extract various harmful substances from the soil. Essential advantages of the sorbent, as well as some other crystalline aluminosilicates showing molecular sorption and ion exchange properties, are: wide spread occurrence, availability, cheapness, granular structure, heat resistance, radiation stability, an ability to chemically and structurally modify the technological characteristics of the mineral. In addition, this sorbent is characterized by high polyfunctionality.
Degree of toxic action of the bore mud depends on their content and properties which are mainly determined by the drilling cuttings characteristics [19]. The main danger of the drilling cuttings is in high content of hydrocarbons which are contained in the payout beds [20]. During the toxicology test, the representatives of hydrobionts Daphnia magna Straus were used. For the biotesting there was applied water extract from the bore mud samples in ratio 1:10. Criterion of the acute toxicity of the extract from daphnia is the death of 50% and more species testing in the samples in comparison with the control (cultivation water) during the period of 48 hours. By the results of carried out testing and water extract dilution factor the class of hazard of the bore mud was determined (table 1) The test water extract from the bore mud has an acute toxic effect on the test objects (Daphnia magna Straus). The dilution factor of water extract of the bore mud, in which there is no harmful effect on the test object is up to 46.13 times, class of hazard for the environment -IV. Water extract from all types of soil has an acute toxic effect on the test objects (Daphnia magna Straus), the hazard class for the environment -IV, while the dilution factor of water extract of the bore mud, in which there is no harmful effect on the test object is up to 2, 7 times. Acute toxicity effect 2,7 IV

Conclusion
The technology is based on the physical-chemical way of drilling wastes utilization by the applying of ecologically safe components directed to the improvement of physical-chemical, hydrophysical and mechanical drilling wastes that will provide decrease of man-induced influence on the natural environment. The soils obtained in the process of bore mud utilization are suitable for reclamation of the adjacent (adjoining) production infrastructure and supporting infrastructure, disturbed lands for temporary and permanent location of oil deposit.